Use Calibre or Pandoc:
pandoc fixed.txt -o okiraku.epub
Use regex in Notepad++ or Sublime Text:
Okiraku Ryoushu no Tanoshii Ryouchi Bouei (The Easygoing Lord’s Enjoyable Territory Defense) is a Japanese web novel series written by Yoshimurada (よしむらだ). It follows the story of a laid-back noble lord who must defend his territory using unconventional, creative, and often humorous strategies. okiraku ryoushu no tanoshii ryouchi bouei raw fix
Add ＃第N話 before each chapter based on the original narou index. Use Calibre or Pandoc :
pandoc fixed